The CEO of Daum Kakao answered police questions Wednesday about accusations that the South Korean mobile messaging service provider failed to take action against child pornography content distributed via its app.

Under South Korean law, child pornography covers anything from abusive imagery of prepubescent children to images simply showing the naked body of someone under 18, if the images were made without consent or in return for reward. Internet service providers are obliged to take appropriate measures to prevent the distribution of such material on their networks. If such content is discovered, the network operators must delete it and stop its distribution immediately, and report it to police.If found in violation of the law, online service providers or their representatives may be sentenced up to 3 years in prison or fined as much as 20 million won (about US$18,000).

The police have been investigating users of Daum Kakao’s messaging app for months.

“We started the investigation on online child pornography since July, and we found that the content was shared by more than 10,000 users of the Kakao Talk, mostly by teenagers,” said Kim Sun-young, chief of the Daejeon Metropolitan Police Agency’s cyber crime investigation squad.

Unless there are technical reasons that make it impossible to monitor a service, the service provider is responsible for monitoring and filtering out lewd content, as well as for reporting it to police, none of which was done by Daum Kakao, Kim said. The police investigation team planned to question the chief executive on those lines, he said, but didn’t give specifics.

This is the first time Korean authorities have accused the operator of a communications service under this law, rather than the user who distributed the content, according to local media reports.

Daum Kakao chief executive officer Lee Sirgoo will diligently comply with the agency’s investigation, the company said in a statement, without commenting further.

The company was formed in October by the merger of South Korean mobile service provider Kakao and of Daum Communications, the country’s second-largest Internet portal. It has faced heat from its users after giving in to a government request for some high-profile users’ private data for surveillance purposes. As a result, many Kakao users switched to a Russian encrypted messenger service, Telegram, which uses servers in Germany. Within a week, it became one of the top downloads in the Korean app market.

Daum Kakao’s chief executive publically apologized to some 35 million local users of messenger app Kakao Talk, and vowed not to compromise users’ privacy in response to requests from authorities. Kakao Talk has about 164 million users around the world, the company claims.

On Monday, the company introduced a similar service to Telegram, a secret chat room that uses end-to-end encryption for all messages. That means the messages cannot be intercepted by outsiders, even if they’re going through its servers, the company said. It also reduced the time of data storage on its servers to between two and three days, down from a maximum of seven days previously.

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